#define  _CRT_SECURE_NO_WARNINGS
#include <stdio.h>
int main()
{
	int a = 0;
	int b = 0;
	int c = 0;

	scanf("%d", &a);

	for (; a != 0;)
	{
		b = a % 10;
		a /= 10;
		c += b;
	}

	printf("%d\n", c);
	return 0;
}
